The electric field probe EFP-07 is a Ag/AgCl (silver/ silver-chloride) electrode.
The electrode can be filled with environmental friendly saturated NaCl or KCl solution (3M NaCl or 3.5 M Kcl).
This electrolyte can be made with 28g/l NaCl (normal salt) in distilled water (pure H2O).
The electrode needs 8-12 hours of pre-soaking in the electrolyte before being used.
Do not use contaminated water or water enhanced with chemical agents. This may seriously degrade the performance of the half-cell and might lead to a damage of the surface.
Measuring the contact resistivities between two electrodes, e.g. when placed in the ground or in an electrolyte bath, will degrade the electrode (cathode (-) and anode (+)). You will irreversible harm the Ag/AgCl electrode. Do not use these electrodes to inject currents!
Tiny currents may not harm.